Counterbalance systems are known in various mechanical assemblies. For example, conventional garage doors include a mechanical torsion spring to act as a counterbalance to reduce the force required to open a garage door. An exemplary torsion spring system includes a torsion spring located on a shaft which is typically located above the door opening. One end of the torsion spring is connected to the shaft. The opposite end of the spring is anchored to the door opening. The torsion spring is preloaded during the installation process. This preloading provides the necessary torque to counterbalance, that is to say, offset the torque the garage door imposes on the shaft by its connection to the drums located on the shaft. These drums are commonly referred to as door drums. The bottom corners of a garage door are connected to the door drums via cables. When the door is opened, the shaft rotates causing the cables to assist the lifting operation and the torsion spring releases its stored energy. When the door is being closed, the cable winds off the drum and the torsion spring assists in offsetting the weight of the door as it is reloaded with energy for the next lifting operation.
Improved counterbalance designs have been developed to replace the mechanical torsion spring. One improved system and method uses a gas spring and a cable drum system. Exemplary improved systems and methods are described in U.S. Pat. No. 6,983,785 issued Jan. 10, 2006 and U.S. Pat. No. 7,537,042 issued May 26, 2009, each of which are hereby incorporated by reference in their entirety, to the extent that either does not conflict with the present application. These improved methods replace the torsion spring with a gas spring and cable drum system. However, all other door components, shaft, door drums located on the shaft, and cables connecting the lower corners of the door to the drums remain required. The gas spring, like the torsion spring, is fixed at one end. However, the opposite end is slideable along a track, rather than able to rotate around the shaft. The slideable end, herein referred to as the slideable carriage, has a pulley to allow a cable to pass around.
When the door is in the closed position a cable wraps fully around a drum, referred to as a drive drum, located on the same shaft to which the door is connected. The spring is fully compressed, when the door is closed, storing the required energy to counterbalance the door. The cable passes from the drive drum around the pulley, attached to the slideable carriage of the spring, and is anchored to a fixed position. This configuration is a 2 to 1 mechanical advantage. For every inch of stroke the gas spring provides 2 inches of cable pull off the drive drum attached to the shaft above the door. Alternatively, for every pound of force the gas spring is applying to the slideable carriage, a half pound of force is applied to the drive drum via the tension in the cable. It is the force in the cable applied to the drive drum that provides the counter torque to offset or balance the torque applied to the shaft by the door weight. When the door is lifted, the compressed gas spring extends by moving the slideable carriage. As the slideable carriage moves, the cable pulls the drive drum applying the counter torque to the shaft. When the door is lowered to the closed position, the spring is again compressed storing the required energy to offset the door weight during the closing operation while reloading the gas spring for the next cycle.
The above-described improvement was advantageous and functional, but other improvements followed. Later developments led to an improved design including a drive drum that could provide the precise torque when coupled to the appropriate gas spring. A system that standardized the components was also developed. This system approximately fixed the number of rotations the shaft made regardless of the door height. By doing so, this improvement reduced the number of different designs of the same component within a garage opener sub-assembly or assembly.
During an installation process of an energy storage device, such as for example, one or more mechanical springs or one or more gas springs, the door will be in the closed position yet the spring will be fully extended. Conversely, to remove or replace the energy storage device, the door will typically be in the closed position, and the one or more springs will be compressed putting the compression cable in tension. Without a compression tool, disconnecting the cable from the slideable carriage can be time-consuming, laborious, and hazardous, even to a well-trained technician.